Fuel pump for diesel engines with air-free injection



J Y March 10, 1936. w. KSTER ET A1.

FUEL PUMP FOR DIESEL ENGINES WITH VAIR FREE INJECTION Filed July 24, 1954 2 Sheets-Sheet 1 AJ www March 10, 1936. w. KSTER E1- AL 2,033,579

FUEL PUMP FOR DIESEL ENGINES WITH AIR FREE INJECTIO'N i?,.Sheets-Sheetl 2 Filed July 24, 1934 amm hasta 1o, 193e' n v 2,033,579v

4UNITED STATI-:s PATENT' OFFICE FUEL PUMP FOB. DIESEL GINES WITH AIB-FREE INJECTION 'wilhelm Kster and August Frankfort-on-the-Main, Germany; said Dussmann assigner to said Kster applicati@ July 24, 1934, serial No. '136,682

. In Germany my ze, 193s s claims. (c1. 10a-44') 'Illere are two types of internal combustion enby means of a cam. If the requirements set gines. In the one fuel and air are mixed during forth 'under l to 4 are to be fulfilled, the pitch the compression stroke of the engine. of the cam must be extremely steep in order to In the other the air for combustion is comattain the desired speed. However, this is re- "5 pressed andmlxed with the'fuel approximately stricted for practical reasons. The maximum 5 at the desired moment of ignition. This type of v has been attained in the known pumps. Further engine is usually called Diesel engine. The inimprovements can only be attained in such fuel jection takes place by means of compressed air. pumps in which a considerable increase of the Objections to this method are the losses due pump plunger speed is possible. As the cam is no l to cooling owing to the injection of air during the longer suilicient, other means must be utilized. 10 combustion, the power required for the injection In the American patent specications 1,864,860 air compressor and ilnally the complicated conand 1,949,789 proposals are set 'forth whichenstruction and high price. dea-vor to fuliill these requirements.

In order to overcome these objections, the'so- The object of the invention is to improve the l called compressorless Diesel engine has been deaction of the injection pump plunger by more l5 velo'ped during the last 2,0 years. In this engine practical arrangement of the operating mecha.- the injection is effected without compressed air, nism as compared with Patent 1,949,789. In that is directly by the fuel pump. both instances the pump plunger is operated by However, the constructions developed during compressed air but it is necessary to introduce dezo the last years possess the drawback as vcoinvices which guarantee the accurate commence- 20 pared with the old Diesel engine that they reprement of the injector, because the period of idle sent a step backwards from a thermic technical movement serves to transmit to the pump plunger point of view in that these engines do no longer live force, which it must impart to the atomiz'lng operate according to the uniform pressure procmechanism when it has attained its maximum ess but according to the detonation process with speed. Onthe one hand the commencement of 25 after-burning. Thus, the constructional 'presthe injection must be accurately controlled and sures increase by to 40%. A lower fuel conon the other hand it must be possible to vary the sumption is not attained and the speciilc cylinder commencement of the injection. output could not be increased. Several embodiments of the invention are illus- I0 All these constructions are only intermediate trated by way of example in the accompanying 30 solutions because in all instances the time is too drawings in which:- long from the preparation of the fuel until the Fig. 1 shows afuel pump in longitudinal section. ignition begins. All these engines must inject 30 Fig. 2 is a diagram showing the travel of the to 45 before the upper dead centre position durpump crank. ,l 85 ing the compression.. In Fig. 3, A and B are diagrams showing the 35 It has been proved that the output of the Diesel compression of the drawn-in air and production engine withouft compressor depends to a grea of the energy. extent upon Fig. 4 is a diagram illustrating the compression 1. The completeness of the atomization, stroke of the pump. 40 2. The smallest attainable' drop size during the Fig. 5 shows in vertical section a pump arrange- 40 atomization, ment, .wherein a single compressor operates a .3. Good distribution in the combustion in such plurality of pump' plungers.

a manner that every minutest drop of fuel is'sur- Fig. 5a is a diagram showing the compression rounded byatoms oi oxygen, p l stroke of the pump illustrated in Fig. 5. 4. 'Ihe shortness of theinjection time. Fig. 6 shows in horizontal section the valve con- 45 'I'he requirements mentioned under 1 to 4 can trol of the pump arrangement illustrated in Fig. 5. be excellently improved by increasing the speed Fig. 'l is a working diagram. of the pump plunger. If this can be considerably Figs. '7a. 7b, and '7c-show the inlet slot oi the augmented, the yarea of the nozzle apertures can rotary valve in'diierent positions. be enlarged. Thus, the/injection period is so Figs.-8a, 8b,v and 8c show the outlet slot'of the 50 greatly reduced that it occupies only a few degrees rotary valve in diierent positions. ofjthe movement of the engine crank. By these Fig. 9 shows in longitudinal section a third measures the requirements mentioned under 1 to l* form of construction of thefuel pump.l 4 can be fullled. The fuel pump according to Fig. 1 comprises a In ordinary fuel pumps the plunger is actuated cylinder casing l surrounding a cylinder la in 55 cylinder C and is, pressed .downwards by the action of a spring 0 so that a valve extension Il sits tightly on a valve seat in the valve plate l. Dur- .ing the outward stroke of the compressor piston 2 the valve I0 is opened as soon as the air pressure in the cylinder la is greater thanE the spring pressure. The compressed air then flows into the air cylinder I and pushes the air piston i upwards with accelerated speed.

Spring l which bears against a plate Il engages the head of a pump plunger I I movable in a pump cylinder I2 having a suction slot I3. The spring l therefore forces the plunger II downwards, thereby drawing fuel into the cylinder I2 through the suction slot i3. As the piston l ascends, it moves the plunger I I upwards, thereby producing the deliverystroke si, sa. l vDuring the first portion n of the delivery stroke the plunger II passes the slot Il, a portion of the fuel drawn in being first returned without appreciable pressure into a suction chamber I I through the slot Il, this portion of the stroke is called the idle movement. The delivery stroke proper sa commences only when the upper edgeof the plungerll has reached the upper edge of the suction slot, this stage being designated the supply movement sa.

After .the compression piston 2 has passed its l upper dead centre position, it moves downwards lated energy on its return stroke carrying air piston l with it under the action of the spring l, the downward movement of the piston I being cushioned by the air compressed in the cylinders l and la between the pistons 2 and 8.

The air imprisoned in the cylinder l after the closing of the valve il is still under pressure.

'111e valve must open exactly at the proper time, and it is consequently necessary for the air pressure between the valve plate 'I and the piston l,

to be neutralized, this being eected through a bore II so that the compressing piston in its lower dead centre position exposes a bore II and establishes communication with the atmospheric air. The valve now closes the slot.

The pump operates in the following manner: l'igs. 2 and 3 show a-b drawing in of fresh Figs. 2, 3, and 4 show b-c compressing of the drawn in air and production of the energy which corresponds to the diagram A, Fig. 3.

e-d idle travel s1 and transmission of energy in the moved pump parts,

d-e injection stroke, a portion of the accumubeing consumed or imparted to the atomiser.

The energy is, however, produced during a longer period lthan the consumption. The time of injection can therefore be considerably reduced without excessively stressing the driving mechanism.

During the idle travel s1 the mass of the-plunger parts is accelerated and attains at the end of the idle travel the speed v max. This speed is braked during the effective compression stroke sz, so that at the end of the pump stroke a speed of v min. prevails. These operations are illustrated in F18. 4. which shows that the injection takes place in anentirelydiiferentmannertothatinthecaseof the hitherto known airless injector methods. The fuel jet is preferably atomized. 'Ihe fuel particles nrst injected into the combustion chainber are therefore rapidly brought to the ignition temperature, so that the retarding of the ignition is reduced, and the thermic efilciency improved.

Figs. 5 and 6 show a pump arrangement, in which only one compressor is provided `for driving several pump plungers and pumps the air into a suitably arranged chamber. The operation of the air piston l and` of the plunger II is the same as in the pump shown in Fig. l. 'Ihe distribution of the operating air is, however, not effected by means of a self controlled valve, but by a mechanically driven rotary valve il, which has an air inlet slot Il and an airoutlet slot 2l. The A compressed operating air flows through a conduit 2| from the compressor into a common chamber 22. A device 23 for shutting oit the air is connected with regulating rods'll in such a manner that the air admission is interrupted in the stop position, so that loss of air cannot o cur when the engine is at a standstill.

From'the control diagrams Figs. 7, q c and 8. a-c the operation of the air distribution can be seen. 4

Fig. 7a shows the air inlet slot Il shortly prior to the opening of the inflow bore |01. The valve Il is'kept closed (a-b) by the spring I until the air pressure is capable of acting without appreciable flow losses. .At b, Fig. 7b. the valve Il opens, so that the air pressure acts on the whole surface of the piston l. At c, Fig. 7c, the air admission is interrupted, the air charge continuing to expand, the piston I being further accelerated. The energy accumulated during the idle travel is converted into atomizing energy at the end of the idle travel .in the manner already described. 'Ihe operation is illustrated in the working diagram Fig. 7. Figs. 8a to 8c show the corresponding position of the outlet slot 2l.

The rotary control valve Il is actuated with the samemeans andatthesamespeedasthe crank shaft l of the pump shown in Fig. 1 is driven. i

Inthepumpsillustratedinll'lgs. 1to4andligs. 5-9 only the air piston 8 carries out the idle travel, whereas the pump plunger is held by a stroke limitation and therefore only participates in the effective pump stroke sz.

By the above described indirect pump actuation, which is merely dependent upon the accumulated energy in the idle travel, many times the output value of the directly driven pump is attained. Therefore several nozzle holes may be employed which improves in a simple manner the quality of the mixture formation. The commencement of the injection can therefore be placed into proximity of the dead centre position. Premature ignitions which stress the engine peril to an abnormal extent and reduce the degree of mechanical efiiciency, are excluded.

The construction illustrated in Fig. 9 shows anv cylinder at the upper end of said air cylinder,

anda pump plunger in sald'pump cylinder connected with said air piston and adapteflto eject fuel from said pump cylinder. said air piston adapted to impart its accelerated movement to said plunger piston, the upper end of said plunger shaped to first check the ejection of fuel from said pump cylinder and then suddenly release the same so that the ejection takes place at maximuml speed.

2. In a fuel pump as specified in claim 1 a lofw pressure chamberand a compression chamber, the end of said plunger cut away at an angle so that during its compression stroke it rst establishes communication between said low pressure chamber and said compression chamber at the commencement of its stroke during which it receives its maximum acceleration before the commencement of the lfuel injection, and then interrupts the communication between said two chambers to commence the fuel injection at maximum speed. 4

3. In a fuel pump for Diesel engines with aircompressor cylinder has attained a certain pressure and then to yield and allow said valve exten- I sion to lift oi! said valve seat and allow the compressed air to enter said air chamber in highly compressed state and accelerate the movement of 'f l. said air piston during its idle stroke, said spring adapted to then retard the movement of said air piston and then again press said extension on to said valve seat, said compressor cylinder having a bore communicatingwlth said air cylinder and` the atmosphere and controlled by said compressor piston, said bore adapted to allow the escapement of the air contlned in saidv air chamber and said spring to act with its full force to press said l extension tightly on to said valve seat.

4. In a fuel pump as specified in claim 1 in which one compressor is provided for operating several 'pump plungers; the combination of a controlslide valve having control grooves -une for each air cylinder, each air cylinder having an inlet and outlet port controlled by said grooves.

5. In a fuel pump as specified in claim 1 inv which one compressor is provided for operatingseveral pump lungers, the combination of a control slide valve having control grooves one for each air cylinder, each air cylinder having an inlet and outlet port controlled by said grooves, a

shut oil element adapted to control the air supply to said control slide, and a pump regulating rod connected with said shut oil element and adapted to automatically close said shut oi'l element when the pump is at-a standstill.

WILHELM Ks'rsa. AUGUST DUssMANN. 

